Blood pressure measuring apparatus and blood pressure measuring method

ABSTRACT

A blood pressure measuring apparatus according to an aspect of the present invention includes: a touch sensor; a pulse wave measurer configured to measure pulse waves from a user; a contact force measurer including at least three force sensors and configured to measure a contact force between the touch sensor and the user by using the at least three force sensors; a contact area measurer configured to measure a contact area between the user and the touch sensor; and a processor configured to determine a vertical direction error, which indicates a degree of deviation of a direction of force, applied by the user to press the touch sensor, from a vertical direction to a surface of the touch sensor based on sensor values sensed by the at least three force sensors, and estimate blood pressure according to a determination result of the vertical direction error based on the pulse waves, the contact force, and the contact area.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority from Korean Patent Application No.10-2018-0028759, filed on Mar. 12, 2018, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference in its entirety.

BACKGROUND 1. Field

Apparatuses and methods consistent with exemplary embodiments relate tocuffless blood pressure monitoring.

2. Description of the Related Art

A pressurized cuff is generally used for measuring blood pressure. Ablood pressure measuring method utilizing the pressurized cuff is anon-continuous measuring method, in which the cuff is inflated so thatan artery is constricted up to around systolic blood pressure, and thenthe pressure in the cuff is slowly released. However, the pressurizedcuff includes a booster pump and the like, such that the cuff isunsuitable for use in a mobile device.

Recently, research is being conducted on a method of cufflesslymeasuring blood pressure in a non-pressure manner without using a cuff,and examples thereof include a blood pressure measuring apparatus usingPulse Transit Time (PTT) and a blood pressure measuring apparatus usingPulse Wave Analysis (PWA). However, the blood pressure measuringapparatus using PTT is inconvenient in that correction is required foreach user to ensure accuracy of measurement; and since bio-signalsshould be measured at two or more locations to measure the pulse wavevelocity, the apparatus cannot be manufactured in a compact size.Further, the blood pressure measuring apparatus using PWA estimatesblood pressure by analyzing only a pulse wave form, such that theapparatus is vulnerable to noise, and blood pressure may not be measuredwith improved accuracy.

SUMMARY

Exemplary embodiments address at least the above problems and/ordisadvantages and other disadvantages not described above. Also, theexemplary embodiments are not required to overcome the disadvantagesdescribed above, and may not overcome any of the problems describedabove.

One or more exemplary embodiments provide an apparatus and a method forcufflessly measuring blood pressure with improved accuracy.

According to an aspect of an exemplary embodiment, there is provided ablood pressure measuring apparatus including: a touch sensor; a pulsewave measurer configured to measure pulse waves from a user; a contactforce measurer including at least three force sensors and configured tomeasure a contact force between the touch sensor and the user by usingthe at least three force sensors; a contact area measurer configured tomeasure a contact area between the user and the touch sensor; and aprocessor configured to determine a vertical direction error, whichindicates a degree of deviation of a direction of force, applied by theuser to press the touch sensor, from a vertical direction to a surfaceof the touch sensor based on sensor values sensed by the at least threeforce sensors, and estimate blood pressure of the user according to adetermination result of the vertical direction error based on the pulsewaves, the contact force, and the contact area.

The pulse waves may include photoplethysmography.

The at least three force sensors may be disposed around the pulse wavemeasurer and positioned at a center of the at least three force sensors

The at least three force sensors may be disposed at an equal distancefrom the pulse wave measurer.

The contact force measurer may measure the contact force between theuser and the touch sensor by adding up or averaging the sensor valuessensed by the at least three force sensors.

The processor may calculate dispersion of the sensor values sensed bythe at least three force sensors, and may determine the verticaldirection error based on the calculated dispersion.

The processor may determine that the vertical direction error increasesas the calculated dispersion increases.

The processor may generate a vertical direction error vector, whichindicates the direction of the force applied by the user to press thetouch sensor, and the degree of the deviation of the direction of forcefrom the vertical direction to the surface of the touch sensor, and maydetermine the vertical direction error based on a magnitude of thegenerated vertical direction error vector.

The processor may determine that the vertical direction error increasesas the magnitude of the vertical direction error vector increases.

In response to the determined vertical direction error being less thanor equal to a predetermined threshold value, the processor may estimateblood pressure of the user based on the measured pulse waves, themeasured contact force, and the measured contact area.

The processor may calculate a contact pressure between the user and thetouch sensor based on the contact force and the contact area, and mayestimate the blood pressure of the user by analyzing a change in thepulse waves according to the contact pressure.

In response to the determined vertical direction error exceeding apredetermined threshold value, the processor may generate guideinformation to guide the user to change the direction of the force tocoincide with the vertical direction, may discard measured values of thepulse wave measurer, the contact force measurer and the contact areameasurer, and may adjust reliability of a pre-estimated blood pressureestimation value.

According to an aspect of another exemplary embodiment, there isprovided a blood pressure measuring method including: sensing contact ofa user with a touch sensor; measuring pulse waves from the user;measuring a contact force between the touch sensor and the user by usingat least three force sensors; measuring a contact area between the userand the touch sensor; determining a vertical direction error, whichindicates a degree of deviation of a direction of force, applied by theuser to press the touch sensor, from a vertical direction to a surfaceof the touch sensor, based on sensor values sensed by the at least threeforce sensors; and estimating blood pressure of the user according to adetermination result of the vertical direction error based on the pulsewaves, the contact force, and the contact area.

The measuring the contact force may include measuring the contact forcebetween the user and the touch sensor by adding up or averaging sensorvalues sensed by the at least three force sensors.

The determining the vertical direction error may include calculatingdispersion of the sensor values sensed by the at least three forcesensors, and determining the vertical direction error based on thecalculated dispersion.

The determining the vertical direction error may include determiningthat the vertical direction error increases as the calculated dispersionincreases.

The determining the vertical direction error may include generating, byusing the sensor values sensed by the at least three force sensors, avertical direction error vector which indicates the direction of theforce applied by the user to press the touch sensor, and the degree ofthe deviation of the direction of force from the vertical direction, anddetermining the vertical direction error based on a magnitude of thegenerated vertical direction error vector.

The determining the vertical direction error may include determiningthat the vertical direction error increases as the magnitude of thevertical direction error vector increases.

The estimating the blood pressure of the user may include, in responseto the determined vertical direction error being less than or equal to apredetermined threshold value, estimating the blood pressure of the userbased on the measured pulse waves, the measured contact force, and themeasured contact area.

The estimating the blood pressure of the user may include, in responseto the determined vertical direction error exceeding a predeterminedthreshold value, generating guide information to guide the user tochange the direction of the force to coincide with the verticaldirection, discarding measured values of the pulse wave measurer, thecontact force measurer, and the contact area measurer, and adjustingreliability of a pre-estimated blood pressure estimation value.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects will be more apparent by describingcertain exemplary embodiments, with reference to the accompanyingdrawings, in which:

FIG. 1 is a block diagram illustrating an example of a blood pressuremeasuring apparatus;

FIGS. 2A, 2B, 2C, and 2D are exemplary diagrams illustrating comparisonof a case where a user presses a touch sensor in a vertical directionwith a case where a user presses a touch sensor in a direction otherthan the vertical direction;

FIG. 3 is an exemplary diagram explaining an arrangement of a pulse wavemeasurer and force sensors;

FIG. 4 is a cross-sectional diagram illustrating an example of a touchsensor;

FIG. 5 is a cross-sectional diagram illustrating another example of atouch sensor;

FIG. 6A is an exploded perspective diagram illustrating yet anotherexample of a touch sensor;

FIG. 6B is a plan view of the touch sensor of FIG. 6A;

FIG. 7 is an exemplary diagram explaining a method of generating avertical direction error vector:

FIG. 8 is a flowchart illustrating an example of a blood pressureestimating method;

FIG. 9 is a flowchart illustrating an example of a method of performingfunctions according to a determination result of a vertical directionerror;

FIG. 10 is a block diagram illustrating another example of a bloodpressure measuring apparatus; and

FIG. 11 is a diagram illustrating a wrist-type wearable device.

DETAILED DESCRIPTION

Exemplary embodiments are described in greater detail below withreference to the accompanying drawings.

In the following description, like drawing reference numerals are usedfor like elements, even in different drawings. The matters defined inthe description, such as detailed construction and elements, areprovided to assist in a comprehensive understanding of the exemplaryembodiments. However, it is apparent that the exemplary embodiments canbe practiced without those specifically defined matters. Also,well-known functions or constructions are not described in detail sincethey would obscure the description with unnecessary detail

Process steps described herein may be performed differently from aspecified order, unless a specified order is clearly stated in thecontext of the disclosure. That is, each step may be performed in aspecified order, at substantially the same time, or in a reverse order.

Further, the terms used throughout this specification are defined inconsideration of the functions according to exemplary embodiments, andcan be varied according to a purpose of a user or manager, or precedentand so on. Therefore, definitions of the terms should be made on thebasis of the overall context.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. Any references to singular may include pluralunless expressly stated otherwise. In the present specification, itshould be understood that the terms, such as ‘including’ or ‘having,’etc., are intended to indicate the existence of the features, numbers,steps, actions, components, parts, or combinations thereof disclosed inthe specification, and are not intended to preclude the possibility thatone or more other features, numbers, steps, actions, components, parts,or combinations thereof may exist or may be added.

Expressions such as “at least one of,” when preceding a list ofelements, modify the entire list of elements and do not modify theindividual elements of the list. For example, the expression, “at leastone of a, b, and c,” should be understood as including only a, only b,only c, both a and b, both a and c, both b and c, or all of a, b, and c.

Further, components that will be described in the specification arediscriminated merely according to functions mainly performed by thecomponents. That is two or more components which will be described latercan be integrated into a single component. Furthermore, a singlecomponent which will be explained later can be separated into two ormore components. Moreover, each component which will be described canadditionally perform some or all of a function executed by anothercomponent in addition to the main function thereof. Some or all of themain function of each component which will be explained can be carriedout by another component. Each component may be implemented as hardware,software, or a combination of both.

FIG. 1 is a block diagram illustrating an example of a blood pressuremeasuring apparatus.

The blood pressure measuring apparatus 100 of FIG. 1 may be implementedas a software module or manufactured in the form of a hardware chip tobe embedded in various types of electronic devices. In this case,examples of the electronic devices may include a cellular phone, asmartphone, a tablet PC, a laptop computer, a personal digital assistant(PDA), a portable multimedia player (PMP), a navigation, an MP3 player,a digital camera, a wearable device, and the like; and examples of thewearable device may include a wristwatch-type wearable device, awristband-type wearable device, a ring-type wearable device, a waistbelt-type wearable device, a necklace-type wearable device, an ankleband-type wearable device, a thigh band-type wearable device, a forearmband-type wearable device, and the like. However, the electronic deviceis not limited to the above examples, and the wearable device is neitherlimited thereto.

Referring to FIG. 1, the blood pressure measuring apparatus 100 includesa touch sensor 110, a pulse wave measurer 120, a contact force measurer130, a contact area measurer 140, and a processor 150.

The touch sensor 110 is disposed at an outermost portion of the bloodpressure measuring apparatus 100 to sense contact of a user's finger. Inone exemplary embodiment, the touch sensor 110 may include acapacitance-type touch sensor.

The touch sensor 110 is disposed above the pulse wave measurer 120, andmay have light transmission properties so that the pulse wave measurer120 may measure a pulse wave signal of a user by transmitting andreceiving light to and from the skin of a user touching the touch sensor110.

A sensor value of the touch sensor 110 may be used to recognize acontact area between the skin of a user and the touch sensor 110, ashape of the contact surface, a center of gravity of the contactsurface, a user's fingerprint, and the like.

The pulse wave measurer 120 is disposed below the touch sensor 110, andmay measure a pulse wave signal of a user. In this case, the pulse wavesignal may include a photoplethysmography signal and the like.

In one exemplary embodiment, when the skin of a user comes into contactwith the touch sensor 110, the pulse wave measurer 120 may measure apulse wave signal of the user by transmitting and receiving light to andfrom the skin of the user touching the touch sensor 110. To this end,the pulse wave measurer 120 may include a light emitter 121 and a lightreceiver 122. For example, the pulse wave measurer 120 may be realizedas an optical spectrometer.

The light emitter 121 may emit light onto the skin of a user when theuser touches the touch sensor 110. The light emitter 121 may include oneor more light sources including a light emitting diode (LED), a laserdiode, a fluorescent body, or the like.

In one exemplary embodiment, each of the light sources may emit avisible ray, a Near Infrared Ray (NIR), or a Mid Infrared Ray (MIR).However, wavelengths of light emitted from the light sources may varydepending on the purpose of measurement or the types of components to beanalyzed. Each of the light sources is not necessarily a singlelight-emitting body, and may be an array including a plurality of lightemitting bodies. Each of the light sources may emit light of the samewavelength, or light of different wavelengths.

The light receiver 122 may receive light reflected or scattered from auser's finger. The light receiver 122 may include one or morephotodetectors including a photo diode, a photo transistor (PTr), acharge-coupled device (CCD), or the like. The photodetector is notnecessarily a single device, but may be an array including a pluralityof devices.

Various numbers and arrangements of light sources and photodetectors maybe provided, and the number and the arrangement thereof may varydepending on the purpose of use of the pulse wave measurer 120 and thesize and shape of the electronic device including the pulse wavemeasurer 120.

The contact force measurer 130 may measure a contact force between theskin of a user and the touch sensor 110. To this end, the contact forcemeasurer 130 may include at least three force sensors 131 which aredisposed below the touch sensor 110 to surround the pulse wave measurer120. For example, if the contact force measurer 130 includes three forcesensors 131, the three force sensors 131 may be disposed at vertices ofa triangle. If the contact force measurer 130 includes four forcesensors 131, the four force sensors 131 may be disposed at vertices of aquadrangle. If the contact force measurer 130 includes five forcesensors 131, the five force sensors 131 may be disposed at vertices of apentagon.

In one exemplary embodiment, the contact force measurer 130 may measurea contact force between the skin of a user and the touch sensor 110 byadding up or averaging sensor values sensed by the at least three forcesensors 131 when the skin of the user comes into contact with the touchsensor 110. The at least three force sensors 131 may be implemented aspiezoelectric force sensors, piezoresistive force sensors, fiberopticcontact-force sensing sensors, and electromagnetic contact force sensingsensors.

The contact area measurer 140 may measure a contact area between theskin of a user and the touch sensor 110. In one exemplary embodiment,the contact area measurer 420 may measure a contact area between theskin of the user and the touch sensor 110 by using sensor values sensedby the touch sensor 110. For example, the contact area measurer 140 mayinclude a capacitive touch sensor to sense the perimeter of a contactarea based on capacitance changes of one or more conductors in the bloodpressure measuring apparatus 100.

The processor 150 may control the overall operations of the bloodpressure measuring apparatus 100.

When the skin of the user comes into contact with the touch sensor 110,the processor 150 may generate guide information for guiding the use toincrease or decrease a contact pressure between the skin of the user andthe touch sensor 110 for measuring blood pressure, and may provide thegenerated guide information to a use through an output device. In thiscase, the output device may include all of a visual output device, anacoustic output device, a tactile output device, and the like.

When the skin of the user comes into contact with the touch sensor 110,the processor 150 may determine a vertical direction error, whichindicates a degree of deviation of a direction of force, applied by theskin of a user to press the touch sensor 110, from a vertical directionto the surface of the touch sensor 110, based on the sensor valuessensed by the at least three force sensors 131 of the contact forcemeasurer 130.

In one exemplary embodiment, the processor 150 may calculate dispersionof the sensor values sensed by the at least three force sensors 131, andmay determine the vertical direction error based on the calculateddispersion. In this case, the processor 150 may determine that thevertical direction error becomes greater as the dispersion increases.

In another exemplary embodiment, by using the sensor values sensed bythe at least three force sensors 131, the processor 150 may generate atwo-dimensional vertical direction error vector, which indicates adirection of force applied by the skin of the user to press the touchsensor 110, and a degree of deviation of the direction of force from avertical direction to the surface of the touch sensor 110, and maydetermine the vertical direction error based on the magnitude of thegenerated vertical direction error vector. In this case, the processor150 may determine that the vertical direction error becomes greater asthe magnitude of the vertical direction error vector increases.

The processor 150 may perform predetermined functions according to adetermination result of the vertical direction error. In this case, thepredetermined functions may include estimating blood pressure,generating and outputting guide information, adjusting reliability of ablood pressure estimation value, discarding measured values andperforming re-measurement, or the like.

In one exemplary embodiment, the processor 150 may compare thedetermined vertical direction error with a predetermined thresholdvalue. Upon comparison, in response to the vertical direction errorbeing less than or equal to the predetermined threshold value, theprocessor 150 may estimate blood pressure of a user based on the pulsewaves measured by the pulse wave measurer 120, the contact forcemeasured by the contact force measurer 130, and the contact areameasured by the contact area measurer 140. More specifically, inresponse to the vertical direction error being less than or equal to thepredetermined threshold value, the processor 150 may calculate a contactpressure (contact pressure=contact force/contact area) between the skinof the user and the touch sensor 110 based on the contact force measuredby the contact force measurer 130 and the contact area measured by thecontact area measurer 140. Further, the processor 150 may estimate bloodpressure of the user by analyzing a change in pulse waves according tothe contact pressure. Blood pressure may include diastolic bloodpressure (DBP), systolic blood pressure (SBP), and mean arterialpressure (MAP); and the contact pressure applied to the skin of the usermay act as an external pressure on blood vessels. In the case where thecontact pressure is lower than the MAP, an elastic restoring force oftissues act to constrict the blood vessels, such that the amplitude ofthe pulse waves is reduced; in the case where the contact pressure isequal to the MAP, the elastic restoring force of tissues becomes zero,having no effect on the blood vessels, such that the amplitude of thepulse waves reaches its peak value. Further, in the case where thecontact pressure is greater than the MAP, the elastic restoring force oftissues act to dilate the blood vessels, such that the amplitude of thepulse waves is reduced. Accordingly, by analyzing the change in pulsewaves according to the contact pressure, the processor 150 may estimate,as the MAP, a contact pressure at a peak amplitude of the pulse waves.Further, the processor 150 may estimate, as the systolic blood pressure(SBP), a contact pressure at a point where an amplitude has a valueequal to a first percentage (e.g., 0.6) of the peak amplitude; and mayestimate, as the diastolic blood pressure (DBP), a contact pressure at apoint where an amplitude has a value equal to a second percentage (e.g.,0.7) of the peak amplitude.

In another exemplary embodiment, the processor 150 may compare thedetermined vertical direction error with a predetermined thresholdvalue. Upon comparison, in response to the vertical direction errorexceeding the predetermined threshold value, the processor 150 maygenerate and output guide information, discard measured values andperform re-measurement, estimate blood pressure and adjust reliabilityof a blood pressure estimation value, or the like. For example, inresponse to the vertical direction error exceeding a predeterminedthreshold value, the processor 150 may generate guide information abouta direction of force to be exerted by the user onto the touch sensor 110so that the direction of force coincides with a vertical direction tothe surface of the touch sensor 110. The processor 150 may provide thegenerated guide information to a user through an output device. In thiscase, the output device may include all of a visual output device, anacoustic output device, a tactile output device, and the like. Inanother example, in response to the vertical direction error exceedingthe predetermined threshold value, the processor 150 may discardmeasured values of the pulse wave measurer 120, the contact forcemeasurer 130, and the contact area measurer 140, and may performre-measurement. In yet another example, even when the vertical directionerror exceeds the predetermined threshold value, the processor 150 mayestimate blood pressure of a user based on the pulse waves measured bythe pulse wave measurer 120, the contact force measured by the contactforce measurer 130, and the contact area measured by the contact areameasurer 140. In this case, the processor 150 may lower the reliabilityof a pre-estimated blood pressure estimation value based on the verticaldirection error. In addition, the processor 150 may adjust thereliability of a blood pressure estimation value according to thevertical direction error by using a correlation model, which representsa correlation between a predetermined vertical direction error and achange in the reliability of a blood pressure estimation value. In thiscase, the correlation model may be provided in the form of amathematical algorithm, but is not limited thereto, and may be providedin the form of a matching table and stored in a storage device.

FIGS. 2A to 2D are exemplary diagrams illustrating comparison of a casewhere a user presses a touch sensor in a vertical direction with a casewhere a user presses a touch sensor in a direction other than thevertical direction. In FIGS. 2A to 2D, left portions illustrate a casewhere a user presses a touch sensor in a vertical direction; and rightportions illustrate a case where a user presses a touch sensor in adirection other than the vertical direction.

Referring to FIGS. 2A to 2D, upon comparing a case where a user pressesa touch sensor in a vertical direction with a case where a user pressesa touch sensor in a direction other than the vertical direction, it canbe seen that there is no significant difference therebetween (see FIG.2B). However, upon comparing pulse waves measured in a case where a userpresses a touch sensor in a vertical direction with pulse waves measuredin a case where a user presses a touch sensor in a direction other thanthe vertical direction, it can be seen that the pulse waves, measured ina case where a user presses a touch sensor in a vertical direction, showa typical oscillometric waveform in which a maximum pulse wave value isfound around the mean blood pressure; by contrast, the pulse waves,measured in a case where a user presses a touch sensor in a directionother than the vertical direction, show an oscillometric waveform inwhich it is difficult to specify the mean blood pressure, as well as thediastolic blood pressure (DBP) or the systolic blood pressure (SBP) (seeFIGS. 2C and 2D).

Accordingly, the blood pressure measuring apparatus 100 may improveaccuracy of blood pressure estimation by evaluating a degree ofdeviation of a direction of force, applied by a user to the touchsensor, from the vertical direction to the surface of the touch sensor,and by inducing the direction of force, applied by the user to the touchsensor, to coincide with the vertical direction to the surface of thetouch sensor.

FIG. 3 is an exemplary diagram explaining an arrangement of a pulse wavemeasurer and force sensors. The dotted line in FIG. 3 indicates that thepulse wave measurer 120 and the force sensors 131 are disposed below thetouch sensor 110.

Referring to FIG. 3, the pulse wave measurer 120 is disposed at thecenter of the touch sensor 110, and three force sensors 131 may bedisposed at each vertex of a triangle, whose center of gravity lies on aposition of the pulse wave measurer 120. In this case, the three forcesensors 131 may be disposed on the same plane, and may be disposed at anequal distance from the pulse wave measurer 120, but the arrangement isnot limited thereto. For example, the pulse wave measurer 120 may bedisposed at a centroid C of the triangle, and x and y coordinates C (x,y) of the centroid C may be obtained as follows:

${C\left( {x,y} \right)} = \left( {\frac{{x\; 1} + {x\; 2} + {x\; 3}}{3},\frac{{y\; 1} + {y\; 2} + {y\; 3}}{3}} \right)$

wherein, x and y coordinate values of the vertices of the triangledenote (x₁, y₁), (x₂, y₂), and (x₃, y₃).

FIG. 4 is a cross-sectional diagram illustrating an example of a touchsensor.

Referring to FIG. 4, the touch sensor 110 may be a capacitance-typetouch sensor. The touch sensor 110 includes a transparent substrate 111,a first transparent electrode 112 and a second transparent electrode 113which are disposed on the transparent substrate 111 and are spaced apartfrom each other, and a transparent cover 114 which covers a top portionof the second transparent substrate 113 while exposing the firsttransparent substrate 112.

The transparent substrate 111 may be made of transparent plastic,transparent glass, or the like, to have light transmission andinsulation properties. The transparent substrate 111 may support thefirst transparent electrode 112 and the second transparent electrode113.

The first transparent electrode 112 and the second transparent electrode113 may be made of transparent conductive material (e.g., Iridium TinOxide (ITO), carbon nanotube, etc.), and may be formed on thetransparent substrate 111. The first transparent electrode 112 isdisposed at the center of the transparent substrate 111, and the secondtransparent electrode 113 may be disposed on the periphery of the firsttransparent electrode 112 while surrounding the first transparentelectrode 112. The first transparent electrode 112 and the secondtransparent electrode 113 may have a predetermined thickness. The firsttransparent electrode 112 functions as a ground electrode, and thesecond transparent electrode 113 functions as a sensing electrode.

The transparent cover 114 may be made of transparent plastic,transparent glass, or the like, to have light transmission andinsulation properties. The transparent cover 114 may be adhered to thetransparent substrate 111 by an adhesive layer while covering the secondtransparent electrode 113 to protect the second transparent electrode113.

Although FIG. 4 illustrates an example where the transparent cover 114covers only the second transparent electrode 113 while exposing thefirst transparent electrode 112, but the transparent cover 114 is notlimited thereto. That is, the transparent cover 114 may be formed tocover the first transparent electrode 113 as well as the secondtransparent electrode 113, to protect both the first transparentelectrode 112 and the second transparent electrode 113.

In the example of FIG. 4, the contact area measurer 140 may measure acontact area of a user's finger 10 as follows.

While a sensing current is supplied to the first transparent electrode112 and the second transparent electrode 113, when a user touches with afinger a top portion of the transparent cover 114 including the firsttransparent electrode 112, a change in capacitance between the firsttransparent electrode 112 and the second transparent electrode 113 mayoccur by the touch of the finger 10 having capacitance. In this case, avalue of change in capacitance may be determined according to a value ofa contact area of the finger 10. As the contact area of the finger 10touching the touch sensor 100 increases, a current flowing to the finger10 also increases, such that a value of change in capacitance betweenthe first transparent electrode 112 and the second transparent electrode113 becomes greater. By contrast, as the contact area of the finger 10touching the touch sensor 110 decreases, a current flowing to the finger10 also decreases, such that a value of change in capacitance betweenthe first transparent electrode 112 and the second transparent electrode113 is lowered. Accordingly, by using a predetermined correlation model,which represents a correlation between a contact area of the finger anda value of change in capacitance, the contact area measurer 140 mayobtain a contact area of the finger 10 according to the value of changein capacitance. In this case, the correlation model may be provided inthe form of a mathematical algorithm, but is not limited thereto, andmay be provided in the form of a matching table and stored in a storagedevice.

FIG. 5 is a cross-sectional diagram illustrating another example of atouch sensor.

Referring to FIG. 5, a touch sensor 110 a includes a transparentsubstrate 111 a, a first transparent electrode 112 a and a secondtransparent electrode 113 a which are formed on a top surface and abottom surface of the transparent substrate 111 a respectively, and atransparent cover 114 a which covers the first transparent electrode 112a and the second transparent electrode 113 a.

The transparent substrate 111 a may be made of transparent plastic,transparent glass, or the like, to have light transmission andinsulation properties. The transparent substrate 111 a may support thefirst transparent electrode 112 a and the second transparent electrode113 a.

The first transparent electrode 112 a and the second transparentelectrode 113 a may be made of transparent conductive material (e.g.,Iridium Tin Oxide (ITO), carbon nanotube, etc.), and may be formed on atop surface and a bottom surface of the transparent substrate 111 arespectively. The first transparent electrode 112 a and the secondtransparent electrode 113 a may have a predetermined thickness. Thefirst transparent electrode 112 a functions as a ground electrode, andthe second transparent electrode 113 a functions as a sensing electrode.

The transparent cover 114 a may be made of transparent plastic,transparent glass, or the like, to have light transmission andinsulation properties. The transparent cover 114 a may cover the firsttransparent electrode 112 a and the second transparent electrode 113 ato protect the first transparent electrode 112 a and the secondtransparent electrode 113 a.

Although FIG. 5 illustrates an example where the first transparentelectrode 112 a and the second transparent electrode 113 a are formed onone transparent substrate 111 a, but the arrangement is not limitedthereto. That is, the second transparent electrode 113 a may be formedon a separate transparent substrate from the transparent substrate 111a. In this case, the transparent cover 114 a covering the secondtransparent electrode 113 a may be omitted.

In the example of FIG. 5, the contact area measurer 140 may measure acontact area of a finger based on a value of change in capacitance whichis generated by the touch of the finger between the first transparentelectrode 112 a and the second transparent electrode 113 a.

FIG. 6A is an exploded perspective diagram illustrating yet anotherexample of a touch sensor, and FIG. 6B is a plan view of the touchsensor of FIG. 6A.

Referring to FIGS. 6A and 6B, the touch sensor 110 b includes atransparent substrate 111 b, sensing lines 112 b arranged in a pluralityof columns on the transparent substrate 111 b, a transparent insulatinglayer 113 b covering the sensing lines 112 b, driving lines 114 barranged in a plurality of rows on the transparent insulating layer 113b, and a transparent cover 115 b covering the driving lines 114 b.

The transparent substrate 111 b may be made of transparent plastic,transparent glass, or the like, to have light transmission andinsulation properties. The transparent substrate 111 b may support thesensing lines 112 b.

The sensing lines 112 b and the driving lines 114 b may be made oftransparent conductive material such as Indium Tin Oxide (ITO), carbonnanotube, and the like. The sensing lines 112 b and the driving lines114 b may intersect with each other to form a grid. An intersectingpoint of the sensing lines 112 b and the driving lines 114 b may be apair of coordinates.

The sensing lines 112 b may have electrode pads which are connected by abridge. Here, each of the electrode pads may be formed in a diamondshape. The bridge may have a much narrower width than the electrodepads. In the same manner as the sensing lines 112 b, the driving lines114 b may have electrode pads which are connected by a bridge. Thesensing lines 112 b and the driving lines 114 b may be arranged so thatthe bridges thereof may intersect with each other. Accordingly, twoelectrode pads of the sensing lines 112 b and two electrode pads of thedriving lines 114 b may be arranged based on intersecting points of thebridges.

The transparent insulating layer 113 b may insulate between the sensinglines 112 b and the driving lines 114 b. The transparent insulatinglayer 113 b may be made of a material having light transmission andinsulation properties.

The transparent cover 115 b may be made of transparent plastic,transparent glass, or the like, to have light transmission andinsulation properties. The transparent cover 115 b may protect thedriving lines 114 b. the transparent cover 115 b may be adhered to thetransparent insulating layer 113 b while covering the driving lines 114b.

In the embodiment of FIGS. 6A and 6B, the contact area measurer 140 maymeasure a contact area of a user's finger as follows.

While a sensing current is sequentially supplied to the driving lines114 b of the touch sensor 110 b, when a user touches with a finger a topportion of the transparent cover 115 b, capacitance may be changed atintersecting points touched by the finger, among intersecting points ofthe sensing lines 112 b and the driving lines 114 b. In this case, thecontact area measurer 140 may obtain coordinates of each of theintersecting points, located at an outermost position, among theintersecting points where capacitance is changed, and may calculate acontact area of the finger based on the obtained coordinate information.

FIG. 7 is an exemplary diagram explaining a method of generating avertical direction error vector. In the exemplary embodiment of FIG. 7,three force sensors are disposed at each vertex of a regular triangle,whose center of gravity lies on a position of a pulse wave measurer.Reference numerals 710, 720, and 730 respectively indicate the positionsof the three force sensors, and reference numeral 740 indicates theposition of the pulse wave measurer.

Once a user's finger touches the position 740 of the pulse wave measurerof the touch sensor, each of the three force sensors disposed at thepositions 710, 720, and 730 may measure a force applied by the finger tothe touch sensor.

Assuming that a sensing value sensed by the first force sensor disposedat the position 710 is 10; a sensing value sensed by the second forcesensor disposed at the position 720 is 20; and a sensing value sensed bythe third force sensor disposed at the position 730 is 14, the processorgenerates a first vector 751, which is directed from the position 740 tothe position 710 and has a magnitude of 10, corresponding to the sensingvalue of 10 sensed by the first force sensor; generates a second vector752, which is directed from the position 740 to the position 720 and hasa magnitude of 20, corresponding to the sensing value of 20 sensed bythe second force sensor; and generates a third vector 753, which isdirected from the position 740 to the position 730 and has a magnitudeof 14, corresponding to the sensing value of 14 sensed by the thirdforce sensor. Then, the processor may generate a vertical directionerror vector 760 by adding up the first vector 751, the second vector752, and the third vector 753. In this case, the direction of thevertical direction error vector 760 may indicate a direction of forceapplied by a user's finger to press the touch sensor; and the magnitudeof the vertical direction error vector 760 may indicate a degree ofdeviation of the direction of force, applied by the finger to press thetouch sensor, from a vertical direction to the surface of the touchsensor.

FIG. 8 is a flowchart illustrating an example of a blood pressureestimating method. The blood pressure estimating method of FIG. 8 may beperformed by the blood pressure estimating apparatus 100 of FIG. 1.

Referring to FIGS. 1 and 8, the blood pressure estimating apparatus 100may sense contact of a user's skin in operation 810 by using the touchsensor 110.

Upon sensing the contact of the user's skin, the blood pressureestimating apparatus 100 may measure pulse waves of a user bytransmitting and receiving light to and from the user's skin touchingthe touch sensor 110 in operation 820; and may measure a contact forcebetween the user's skin and the touch sensor 110 by using at least threeforce sensors 131 in operation 830. For example, by adding up oraveraging sensor values sensed by the at least three force sensors 131,the blood pressure estimating apparatus 100 may measure the contactforce between the user's skin and the touch sensor 110.

The blood pressure estimating apparatus 100 may measure a contact areabetween the user's skin and the touch sensor 110 by using the sensorvalues sensed by the touch sensor 110 in operation 840. The method ofmeasuring the contact area between the user's skin and the touch sensor110 by the blood pressure estimating apparatus 100 is described abovewith reference to FIGS. 4 to 6B, such that detailed description thereofwill be omitted.

By using the sensor values sensed by the at least three force sensors131, the blood pressure estimating apparatus 100 may determine avertical direction error which indicates a degree of deviation of adirection of force, applied by the user's skin to press the touch sensor110, from a vertical direction to the surface of the touch sensor 110 inoperation 850. For example, the blood pressure estimating apparatus 100may calculate dispersion of the sensor values sensed by the at leastthree force sensors 131, and may determine the vertical direction errorbased on the calculated dispersion. In this case, the blood pressureestimating apparatus 100 may determine that the vertical direction errorbecomes greater as the dispersion increases. In another example, byusing the sensor values sensed by the at least three force sensors 131,the blood pressure estimating apparatus 100 may generate a verticaldirection error vector which indicates a direction of force applied bythe skin of the user to press the touch sensor 110, and a degree ofdeviation of the direction of force from a vertical direction to thesurface of the touch sensor 110, and may determine the verticaldirection error based on the magnitude of the generated verticaldirection error vector. In this case, the blood pressure estimatingapparatus 100 may determine that the vertical direction error becomesgreater as the magnitude of the vertical direction error vectorincreases.

The blood pressure estimating apparatus 100 may perform predeterminedfunctions according to a determination result of the vertical directionerror in operation 860. In this case, the predetermined functions mayinclude estimating blood pressure, generating and outputting guideinformation, adjusting reliability of a blood pressure estimation value,discarding measured values and performing re-measurement, or the like.

FIG. 9 is a flowchart illustrating an example of a method of performingfunctions according to a determination result of a vertical directionerror, which may be an example of the operation 860 of FIG. 8.

Referring to FIGS. 1 and 9, the blood pressure estimating apparatus 100may compare a vertical direction error with a predetermined thresholdvalue in operation 910. In this case, the predetermined threshold valuemay be preset according to performance and purpose of use of the bloodpressure estimating apparatus 100.

In response to the vertical direction error being less than or equal tothe predetermined threshold value, the blood pressure estimatingapparatus 100 may estimate blood pressure of a user based on themeasured pulse waves, the measured contact force, and the measuredcontact area in operation 920. For example, in response to the verticaldirection error being less than or equal to the predetermined thresholdvalue, the blood pressure estimating apparatus 100 may calculate acontact pressure (contact pressure=contact force/contact area) betweenthe skin of the user and the touch sensor 110 based on the measuredcontact force and the measured contact area, and may estimate bloodpressure of the user by analyzing a change in pulse waves according tothe contact pressure.

In response to the vertical direction error exceeding the predeterminedthreshold value, the blood pressure estimating apparatus 100 maygenerate and output guide information, discard measured values andperform re-measurement, estimate blood pressure and adjust reliabilityof a blood pressure estimation value, or the like in operation 940. Forexample, in response to the vertical direction error exceeding thepredetermined threshold value, the blood pressure estimating apparatus100 may generate guide information for guiding a direction of force,applied by the skin of the user to press the touch sensor 110, tocoincide with a vertical direction to the surface of the touch sensor110, and may provide the generated guide information to a user throughan output device. In another example, in response to the verticaldirection error exceeding the predetermined threshold value, the bloodpressure estimating apparatus 100 may discard measured values (e.g., themeasured pulse waves, the measured contact force, the measured contactarea, etc.), and may perform re-measurement. In yet another example,even when the vertical direction error exceeds the predeterminedthreshold value, the blood pressure estimating apparatus 100 may measureblood pressure of the user based on the measured pulse waves, themeasured contact force, and the measured contact area. In this case, theblood pressure estimating apparatus 100 may adjust reliability of apre-estimated blood pressure estimation value based on the verticaldirection error.

FIG. 10 is a block diagram illustrating another example of a bloodpressure measuring apparatus.

Referring to FIG. 10, the blood pressure measuring apparatus 1000includes a touch sensor 110, a pulse wave measurer 120, a contact forcemeasurer 130, a contact area measurer 140, a processor 150, afingerprint recognizer 1010, an input part (e.g., an input interface)1020, an output part (e.g., an output interface) 1030, a communicator(e.g., a communication interface) 1040, and a storage part (e.g., astorage or memory) 1050. Here, the touch sensor 110, the pulse wavemeasurer 120, the contact force measurer 130, the contact area measurer140, and the processor 150 are described above with reference to FIG. 1,such that detailed description thereof will be omitted.

The fingerprint recognizer 1010 may recognize a fingerprint of acontacting portion of a user's skin touching the touch sensor 110. Inone exemplary embodiment, the fingerprint recognizer 1010 may recognizea ridge and a valley of the contacting portion of a finger by usingsensor values sensed by the touch sensor 110, and may recognize afingerprint of a contacting portion of the user's skin based on therecognized ridge and valley. In this case, the processor 150 mayidentify a user by comparing the recognized fingerprint with pre-storedfingerprint data, and may store blood pressure information, measured forthe user, in the storage part 1050 as information of the user.

The input part 1020 may receive input of various operation signals froma user. In one embodiment, the input part 1020 may include a keypad, adome switch, a touch pad (static pressure/capacitance), a jog wheel, ajog switch, a hardware (H/W) button, and the like. Particularly, thetouch pad, which forms a layer structure with a display, may be called atouch screen.

The input part 1020 may receive input of user-related information. Inthis case, the user-related information may include height, weight, age,and the like. Based on the input user-related information, the processor150 may correct blood pressure. A suitable blood pressure estimationcorrelation model may be stored for each user in the storage part 1050,and the processor 150 may correct blood pressure by selecting a bloodpressure correlation model, which is suitable for a corresponding user,from the storage part 1050.

The output part 1030 may output data input by a user, data obtained orprocessed by blood pressure measuring apparatus 1000, and informationrequired for processing data of the blood pressure measuring apparatus1000, and the like. In one embodiment, the output part 1030 may outputthe data input by a user, the data obtained or processed by bloodpressure measuring apparatus 1000, and the information required forprocessing data of the blood pressure measuring apparatus 1000, and thelike by using at least one of an acoustic method, a visual method, and atactile method. To this end, the output part 1030 may include a display,a speaker, a vibrator, and the like.

The communicator 1040 may perform communication with an external device.For example, the communicator 1040 may transmit, to the external device,the data input by a user, the data obtained or processed by bloodpressure measuring apparatus 1000, and the information required forprocessing data of the blood pressure measuring apparatus 1000, and thelike; or may receive, from the external device, various data useful forestimation of blood pressure.

In this case, the external device may be medical equipment using thedata input by a user, the data obtained or processed by blood pressuremeasuring apparatus 1000, and the information required for processingdata of the blood pressure measuring apparatus 1000, and the like, aprinter to print out results, or a display to display the results. Inaddition, the external device may be a digital TV, a desktop computer, acellular phone, a smartphone, a tablet PC, a laptop computer, a personaldigital assistant (PDA), a portable multimedia player (PMP), anavigation, an MP3 player, a digital camera, a wearable device, and thelike, but is not limited thereto.

The communicator 1040 may communicate with an external device by usingBluetooth communication, Bluetooth Low Energy (BLE) communication, NearField Communication (NFC), WLAN communication, Zigbee communication,Infrared Data Association (IrDA) communication, Wi-Fi Direct (WFD)communication, Ultra-Wideband (UWB) communication, Ant+ communication,WIFI communication, Radio Frequency Identification (RFID) communication,3G communication, 4G communication, 5G communication, and the like.However, this is merely exemplary and is not intended to be limiting.

The storage part 1050 may store programs or commands for operation ofthe blood pressure measuring apparatus 1000, and may store data input toand output from the blood pressure measuring apparatus 1000. Further,the storage part 1050 may store the data input by a user, the dataobtained or processed by blood pressure measuring apparatus 1000, andthe information required for processing data of the blood pressuremeasuring apparatus 1000, and the like.

The storage part 1050 may include at least one storage medium of a flashmemory type memory, a hard disk type memory, a multimedia card microtype memory, a card type memory (e.g., an SD memory, an XD memory,etc.), a Random Access Memory (RAM), a Static Random Access Memory(SRAM), a Read Only Memory (ROM), an Electrically Erasable ProgrammableRead Only Memory (EEPROM), a Programmable Read Only Memory (PROM), amagnetic memory, a magnetic disk, and an optical disk, and the like.Further, the blood pressure measuring apparatus 1000 may operate anexternal storage medium, such as web storage and the like, whichperforms a storage function of the storage part 1050 on the Internet.

FIG. 11 is a diagram illustrating a wrist-type wearable device.

Referring to FIG. 11, the wrist-type wearable device 1100 includes astrap 1110 and a main body 1120.

The strap 1110 may be connected at both sides of the main body 1120, andboth ends of the strap 1110 may be detachably fastened to each other, ormay be integrally formed as a smart band strap. The strap 1110 may bemade of a flexible material to wrap around a user's wrist so that themain body 1120 may be worn around a user's wrist.

The main body 1120 may include the above-described blood pressureestimating apparatuses 100 and 1000. Further, the main body 1120 mayinclude a battery which supplies power to the wrist-type wearable device1100 and the blood pressure estimating apparatuses 100 and 1000.

The touch sensor may be mounted at the top of the main body 1120 to beexposed so that a user's finger may easily touch the touch sensor.However, the touch sensor is not limited thereto, and may be mounted atthe strap 1110.

The wrist-type wearable device 1100 may further include a display 1121and an input part 1122 which are mounted at the main body 1120. Thedisplay 1121 may display data processed by the wrist-type wearabledevice 1100 and the blood pressure estimating apparatuses 100 and 1000,processing result data, and the like thereof. The input part 1122 mayreceive input of various operation signals from a user.

While not restricted thereto, an exemplary embodiment can be embodied ascomputer-readable code on a computer-readable recording medium. Thecomputer-readable recording medium is any data storage device that canstore data that can be thereafter read by a computer system. Examples ofthe computer-readable recording medium include read-only memory (ROM),random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, andoptical data storage devices. The computer-readable recording medium canalso be distributed over network-coupled computer systems so that thecomputer-readable code is stored and executed in a distributed fashion.Also, an exemplary embodiment may be written as a computer programtransmitted over a computer-readable transmission medium, such as acarrier wave, and received and implemented in general-use orspecial-purpose digital computers that execute the programs. Moreover,it is understood that in exemplary embodiments, one or more units of theabove-described apparatuses and devices can include circuitry, aprocessor, a microprocessor, etc., and may execute a computer programstored in a computer-readable medium.

The foregoing exemplary embodiments are merely exemplary and are not tobe construed as limiting. The present teaching can be readily applied toother types of apparatuses. Also, the description of the exemplaryembodiments is intended to be illustrative, and not to limit the scopeof the claims, and many alternatives, modifications, and variations willbe apparent to those skilled in the art.

What is claimed is:
 1. A blood pressure measuring apparatus, comprising:a touch sensor configured to measure a contact area between a user andthe touch sensor; a contact force measurer comprising at least threeforce sensors disposed at, at least three different positions, andconfigured to measure a contact force between the touch sensor and theuser by using the at least three force sensors, wherein the least threeforce sensors comprises a first force sensor disposed at a firstposition and configured to measure a first vector directed from acentroid of the at least three different positions of the least threeforce sensors to the first position, a second force sensor disposed at asecond position and configured to measure a second vector directed fromthe centroid to the second position, and a third force sensor disposedat a third position and configured to measure a third vector directedfrom the centroid to the third position; a photoplethysmography (PPG)sensor disposed at the centroid of the at least three differentpositions of the at least three force sensors, and configured to obtaina PPG signal while the contact force is being applied between the touchsensor and the user; and a processor configured to determine a verticaldirection error which indicates a degree of deviation of a direction ofthe contact force from a vertical direction to a surface of the touchsensor, by adding the first vector, the second vector and the thirdvector of the first force sensor, the second force sensor, and the thirdforce sensor, and in response to the vertical direction error being lessthan or equal to a predetermined threshold value, activate the PPGsensor located at the centroid of the first force sensor, the secondforce sensor, and the third force sensor, and estimate blood pressurebased on the PPG signal; and a ratio of the contact force to the contactarea.
 2. The blood pressure measuring apparatus of claim 1, wherein theat least three force sensors are disposed at an equal distance from thePPG sensor.
 3. The blood pressure measuring apparatus of claim 1,wherein the contact force measurer is further configured to measure thecontact force between the user and the touch sensor by adding up oraveraging the first vector, the second vector, and the third vector. 4.The blood pressure measuring apparatus of claim 1, wherein the touchsensor comprises: a transparent substrate; a first transparent electrodeand a second transparent electrode that are disposed on the transparentsubstrate and are spaced apart from each other; and a transparent coverthat covers a top portion of the second transparent electrode whileexposing the first transparent electrode.
 5. The blood pressuremeasuring apparatus of claim 1, wherein the processor is furtherconfigured to generate a vertical direction error vector, whichindicates the direction of the contact force applied by the user topress the touch sensor, and the degree of deviation of the direction ofthe contact force from the vertical direction, and determine thevertical direction error based on a magnitude of the generated verticaldirection error vector.
 6. The blood pressure measuring apparatus ofclaim 1, wherein the touch sensor comprises: a transparent substrate; afirst transparent electrode and a second transparent electrode that aredisposed on a top surface and a bottom surface of the transparentsubstrate, respectively, so that the transparent substrate is placedbetween the first transparent electrode and the second transparentelectrode; and a transparent cover that covers an outer surface of thefirst transparent electrode and an outer surface of the secondtransparent electrode.
 7. The blood pressure measuring apparatus ofclaim 1, wherein the processor is further configured to estimate theblood pressure of the user by analyzing a change in the PPG signalaccording to a contact pressure that corresponds to the ratio of thecontact force to the contact area.
 8. The blood pressure measuringapparatus of claim 1, wherein in response to the determined verticaldirection error exceeding the predetermined threshold value, theprocessor is further configured to generate guide information to guidethe user to change the direction of the force to coincide with thevertical direction, and discard the PPG signal that is obtained at atime when the contact force is applied, and adjust reliability of theestimated blood pressure.
 9. A blood pressure measuring method,comprising: sensing contact of a user with a touch sensor; measuring acontact force between the touch sensor and the user by using at leastthree force sensors disposed at, at least three different positions,wherein the at least three force sensors comprises a first force sensor,a second force sensor, and a third force sensor, and wherein themeasuring the contact force comprises: measuring, by the first forcesensor disposed at a first position, a first vector directed from acentroid of the at least three different positions of the least threeforce sensors to the first position, measuring, by the second forcesensor disposed at a second position, a second vector directed from thecentroid to the second position; and measuring, by the third forcesensor disposed at a third position, a third vector directed from thecentroid to the third position; measuring a photoplethysmography (PPG)signal from the user by a PPG sensor disposed at the centroid of the atleast three different position of the at least three force sensors,while the contact force is being applied between the touch sensor andthe user; measuring a contact area between the user and the touchsensor; determining a vertical direction error which indicates a degreeof deviation of a direction of the contact force from a verticaldirection to a surface of the touch sensor, by adding the first vector,the second vector and the third vector of the first force sensor, thesecond force sensor, and the third force sensor; and in response to thevertical direction error being less than or equal to a predeterminedthreshold value, estimating blood pressure of the user according to adetermination result of the vertical direction error based on the PPGsignal of the PPG sensor located at the centroid of the first forcesensor, the second force sensor, and the third force sensor, and a ratioof the contact force to the contact area.
 10. The blood pressuremeasuring method of claim 9, wherein the vertical direction errorincreases as the degree of deviation increases.
 11. The blood pressuremeasuring method of claim 9, wherein the vertical direction errorincreases as a magnitude of a combination of the first vector, thesecond vector, and the third vector.
 12. The blood pressure measuringmethod of claim 9, wherein the estimating the blood pressure of the usercomprises, in response to the vertical direction error exceeding thepredetermined threshold value, generating guide information to guide theuser to change the direction of the contact force to coincide with thevertical direction, discarding the PPG signal that is obtain at a timewhen the contact force is applied, and adjusting reliability of theestimated blood pressure.